Add test for subclassing Date

test/built-ins/Date/subclassing.js

@@ -0,0 +1,55 @@
+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-date-value
+es6id: 20.3.2.2
+description: Error retrieving `Symbol.toPrimitive` method from object value
+info: |
+  3. If NewTarget is not undefined, then
+     [...]
+     c. Let O be ? OrdinaryCreateFromConstructor(NewTarget, "%DatePrototype%",
+        « [[DateValue]] »).
+     [...]
+
+  OrdinaryCreateFromConstructor ( constructor, intrinsicDefaultProto [ ,
+  internalSlotsList ] )
+
+  [...]
+  2. Let proto be ? GetPrototypeFromConstructor(constructor,
+     intrinsicDefaultProto).
+  3. Return ObjectCreate(proto, internalSlotsList).
+features: [Reflect]
+---*/
+
+var callCount = 0;
+var Ctor = function() {
+  callCount += 1;
+};
+var instance;
+
+instance = Reflect.construct(Date, [64], Ctor);
+
+assert.sameValue(
+  Object.getPrototypeOf(instance),
+  Ctor.prototype,
+  'constructor defines an object `prototype` property'
+);
+assert.sameValue(callCount, 0, 'constructor not invoked');
+assert.sameValue(
+  Date.prototype.getTime.call(instance),
+  64,
+  'proper subclass has a [[DateValue]] slot'
+);
+
+Ctor.prototype = null;
+instance = Reflect.construct(Date, [64], Ctor);
+
+assert.sameValue(
+  Object.getPrototypeOf(instance),
+  Date.prototype,
+  'constructor does not defines an object `prototype` property'
+);
+assert.sameValue(callCount, 0, 'constructor not invoked');
+assert.sameValue(
+  instance.getTime(), 64, 'direct instance has a [[DateValue]] slot'
+);